Method and apparatus for grinding



Jan. 10, 1956 F. G. KRAFFT 2,729,919

METHOD AND APPARATUS FOR GRINDING Filed Sept. 6, 1952 6 Sheets-Sheet llNVENTQR REDERICK G.KRAFF ATTORNEYS "A a v A Q ////X Jan. 10, 1956 FiledSept. 6, 1952 F. G. KRAFFT METHOD AND APPARATUS FOR GRINDING 6Sheets-Sheet I2 Jan. 10, 1956 F. G. KRAFFT METHOD AND APPARATUS FORGRINDING 6 Sheets-Sheet 5 Filed Sept. 6, 1952 FIG-ll R o T N E V NFREDERICK G. KRAFFT ATTORNEYS Jan. 10, 1956 F. G. KRAFFT METHOD ANDAPPARATUS FOR GRINDING Filed Sept. 6, 1952 6 Sheets-Sheet 4 FIG-9INVENTOR FREDERICK G. KRAFFT ATTORNEYS Jan. 10, 1956 F. cs. KRAFFT2,729,919

METHOD AND APPARATUS FOR GRINDING Filed Sept. 6, 1952 6 Sheets-Sheet 5INVENTOR FREDERICK G. KR AFFT BYTWQ 7" k ATTORNEYS Jan. 10, 1956 F. G.KRAFFT 2,729,919

METHOD AND APPARATUS FOR GRINDING Filed Sept. 6, 1952 6 Sheets-Sheet 6INVENTOR F DERICK G. KRAFFT ATTORNEYS United States Patent 2,729,919METHOD AND APPARATUS FOR GRINDING Frederick G. Kralft, Springfield,Ohio, assiguor to The Thompson Grinder Company, Springfield, Ohio, acorporation of Ohio Application September 6, 1952, Serial No. 308,265

25 Claims. (Cl. 51-92) This invention relates to a method and apparatusfor grinding, and particularly to such a method and apparatus inconnection with producing oil spots on bearing surfaces, and forproducing similar regular patterns of spots on other surfaces for thepurpose of either retaining lubricant or being decorative, or both.

In the manufacture of machine tools and the like, particularly grinders,planers, shapers, lathes, and similar organizations, there is at leastone reciprocating part that slides on machined ways. These ways must bevery carefully machined to make them perfectly true and smooth I inorder that the part reciprocating thereon will be guided thereby in aperfectly true path.

While the forming of the ways and the bearing surfaces on the parts thatrest thereon to perfectly true and exactly mating surfaces is arelatively simple task utilizing modern machinery and modern methods,the very perfection to which these interengaging surfaces are formedmakes it necessary to provide some means of supplying lubricant theretoso that the surfaces do not run dry in operation. When the surfaces areground to a smooth finish, then the relative reciprocation of the waysand the part supported thereon strips the bearings surfaces of alllubricant, and not only does this make it more difficult to reciprocatethe said part, but chattering may occur, seriously detracting from theworkpieces being machined, and serious damage to the bearing surfaces ofthe part and the ways can occur because of the lack of lubricantthereon.

It is the practice in connection with the sliding bearing surfaces ofsuch machine elements to perform a spotting operation thereon to providesmall depressions in the way, for retaining lubricant to avoid thedrawbacks referred to above. While this is a standard procedure inconnection not only with the ways of machine tools, but also for surfaceplates, and the like, it is nevertheless, an extremely slow andexpensive operation, and there is absolutely no way of insuring that thespot pattern is uniform over the entire area spotted, or that theindividual spots will present even a fair degree of uniformity.

For this reason, many hand spotted ways are defective in that too littlelubrication is provided at one point, while too much may be provided atanother point, thereby providing an opportunity for inaccuracy in theoperation of the machine.

In certain instances, ways of the nature described are not spotted, butthe retaining of the lubricant is taken care of by the bearing surfacesof the reciprocating memher which are either spotted or which may onlybe rough ground. In this case, the spotted or lubricant retainingsurface is invisible and the ways themselves are ground to an extremelysmooth uniform finish.

In the last instance mentioned above, it is important that the Ways givean absolutely uniform appearance and the grinding thereof is thereforean extremely critical operation, with the result that there isconsiderable scrap in connection with this particular portion ofmanufacturing the machine.

Another extremely important reason why the hand spotting of ways is notalways entirely satisfactory is that a great many machine tool ways aremade of hardened material, either by hardening the way area directly onthe machine, of which the way is a part, or by machining the way as aseparate member and thereafter assembling it with the machine tool. Inthis case, it is practically im possible to accomplish any sort ofsatisfactory hand scraping operation that will provide the spots on theway for retaining lubricant.

Having the foregoing in mind, the particular object of the presentinvention is to provide a method and apparatus for spotting bearingsurfaces, such as machine tool ways, in such a manner as to eliminatethe hand labor previously employed in this operation.

Still another object is the provision of a method and apparatus forspotting machine tool ways which will produce an absolutely uniform andunvarying pattern of spots thereon.

It is also an object of this invention to provide a method and apparatusfor imparting a surface configuration to a work member such as a machinetool way which gives the said way an attractive appearance by virtue ofthe absolutely uniform pattern of spots, and which will prevent thescrapping of work members because of minor and mechanicallyinconsequential surface blemishes.

Another object is the provision of a novel type of abrading memberparticularly useful in carrying out the method of my invention.

A still further particular object is the provision of a work memberparticularly adapted for use as a machine tool way and characterized inthe provision on the working surface thereof of an arrangement of oilspots formed thereon in accordance with the teachings of my invention.

-These and other objects and advantages will become more apparent uponreference to the following description taken in connection with theaccompanying drawings, in

which Figure 1 is a perspective view of a grinding machine set up forcarrying out the method of this invention;

Figure 2 is a more or less diagrammatic view showing the hydraulicoperating circuit for the machine of Figure 1;

Figure 3 is a fragment of a bearing surface which has been spotted inthe machine of Figure l in accordance with the teachings of myinvention;

Figure 4 is an exploded perspective view of one form of wheel which Ihave constructed according to my invention;

. Figure 5 is a transverse sectional view through the wheel and may beindicated by cutting plane 5-5-5 on Figure 4;

Figure 6 is a vertical longitudinal section taken through the wheel withthe abrasive segments removed and showing only the support portions ofthe wheel;

Figure 7 is a view of the assembled wheel of Figures 4 and 5 looking infrom the left side of the wheel as it is viewed in Figure. 5;

Figure 8 is a view showing the top portion of the wheel of Figure 7 atconsiderably enlarged scale;

Figure 9 is a development showing substantially the path which any oneof the abrasive segments of the wheel of Figures 4 and 5 takes;

Figure 10 is a diagrammatic view provided for the purpose ofillustrating the manner in which the abrasive segments are arranged inthe wheel of Figures 4 and 5;

Figure 11 is a fragmentary sectional view showing a wheel having thesame characteristics as the Wheel of Figures 4 and 5, except that theabrasive segments are permanently bonded into the body of the wheel;

Figure 12 is a fragmentary sectional view indicated by line 1212 onFigure 3 showing a number of the spots on the workpiece in cross-sectionand illustrating the uniformity of configuration and spacing thereof;

Figure l3 is a -fragmente'try view showing one of the oil spots inFigure 12 drawn at greatly enlarged scale; showing how the ends of thespots are tapered out so that no burrs are formed; I I

Figure i4 is a fragmentary perspective view showing a V=way spottedaccording to my invention;

Figure is a perspective view showing a wheel adapted for spotting the V-way of Figure 14;

Figure 16 is a perspective view of a modification wherein the hub orholder is formed'with a helical groove there in and the abrasive"element is inserted therein in the form of substantially circularsegments; v

Figure 17 is a view of the Figure 16 modification, but showing theabrasive segments partially inserted in "the hub;

Figure 18 is a view showing the ot pattern imparted to soon; member bythe Figures .16 and "17 arran ement;

Figure 19 is a side elevational view of a modification showing agrinding 'wh'eel tonned in a manner to provide spots on a work me berground thereby;

Figure 20 is a view of another modification similar to Figure 19;

Figure 21 is a view looking down on a workpiece which has been groundwith one of the wheels of Figures 19 or 20, showing a typical spotpattern imparted to the workpiece by the wheel; and

Figure 22 is a perspective view more or less diagrammaticallyillustrating the manner in which the individual portions of the wheelsofFigures 1'9 and 20 operate to form the spot pattern on the workpiece.

General arrangement My invention is practiced by providing an abrasivemember having an interrupted work engaging surface thereon, and movingthe working surface of the abrading member and the surface that is to bespotted relatively at a predetermined speed. According to one form of myinvention, the abrading member comprises projecting ribs extendinggenerally helically thereabout, one right hand, and one left hand, andwith each rib interrupted at each alternate point of intersectionthereof with the other rib. When the abrading member is rotated at apredetermined constant velocity and the work member to be spotted isreciprocated relative thereto at a predetermined velocity, one singlepass of the abrading member across the surface of the Work member willprovide for the spot pattern desired.

According to another form which my invention can take, instead offorming right and left hand helical ribs on the wheel, the wheel can beformed with right and left hand helical grooves and the spot patternimparted to the workpiece is formed by the raised portions of the wheel"between the grooves.

Structural arrangement Referring to the drawings somewhat more indetail, the machine illustrated in Figure 1 comprises a bed 10 havingreciprocably mounted thereon a table '12 on which the work member W tobe operated is mounted.

A column 14 adjacent bed 10 supports a wheelhead As is diagrammaticallyillustrated in Figure 2, abrading member 18 has connected thereto theconstant speed motor 20 for driving the abrading' member at apredetermined rotational speed.

Figure 2 also indicates that the reciprocating table 12 is connectedwith the reciprocating hydraulic motor 22 in bed 10 which ishydraulically connected with pump '24 by reversing valve 26. A flowcontrol valve 28 may be provided in the pump discharge line forregulating the fluid now to motor 22, whereby the linear velocity oftable 12, and, therefore, of work member W, can be regulat'cd.

Figure 3 illustrates a port-ion of work member W after the surfacethereof has been spotted according to this invention; The direction ofmovement of work member W in Figure 3 is indicated by arrow 30. Thesurface of the workpiece of Figure 3 will be seen to contain a firstgroup of diagonal lines of spots 32 and a second group of diagonal linesof spots 34, with the spots being spaced from each other. However, eventhough the spots are spaced from each other, a straight line drawnacross the surface in any direction will intersect at plurality of thespots so that it will be seen that if lubricant were contained in thespots, the complete surface of a member supported on the spotted surfacewould be lubricated.

It will also be noted in Figure 3 that the spots are absolutely uniformas to individual size and spacing so that absolutely uniform lubricationof the surface is had, as well as there being uniform bearing surfacepresented for supporting any member that is mounted on the spottedsurface.

it will be understood that the spot pattern illustrated in Figure 3 isonly representative of a great many different patterns that can beformed in accordance with this invention. The particular pattern shownin Figure 3 lends itself well to being formed by an abrading member thatcan be constructed in a convenient manner, but many modifications in thestructure of the abrading member are contemplated, and thesemodifications would lead to varying pattern forms.

The abrading member which I employ for obtaining the spot pattern ofFigure 3 is illustrated in detail in Figures 4 through 10. Turning firstto Figure 6, the spindle of the Wheelhead bears reference numeral 36,and mounted thereon is a Wheel hub 38 having a radial flange 46) at thespindle end of the hub. Adapted for being closely received about theoutersurface of cylindrical hub 38 are a plurality of wedge-shapedsegments 42 having their widest part at the top in Figure 6 and arrangedtherebetween are identically shaped wedge segments 44 having theirwidest parts at the bottom.

The wedge members 42 and 44 are conveniently formed by being made fiaton their opposite sides by grinding in a surface grinder. As will beseen hereinafter, this particular manner of forming the wedge plates 42and 44 contributes to the particular configuration of the spots in thespot pattern of Figure 3, and that the spots could be varied inconfiguration by changing the manner of forming wedge members 42 and 44so that instead of their opposite faces being flat, they would bearcuatc in con iguration. I

in Figure 6 at the right side of the view, in direct en ga'g'einent withradial flange 4t! is a wedge member 46 with its thiclt side at thebottom, and which thick side is only one-half the thickness of the thicksides of the Wedge members 42 and 44. The thin wed e member 46 isprovided so that when the wheel is assembled, the wedge members 42 and44 will be positioned vertically to theaxis of rotation of the ab'radingmember.

At the extreme left side of Figure 6 is a clamping ring 48 and inengagement with the right face of this clampin'g ri'ng is a second thinwedge member 50, exactly like wedge member 46, except that it's thickpart is at the top. A number of bolts 52 may be provided for clampingthe entire assembly together, and the provision of wedge member 50insures that clamping ring 48 will be positioned'in a plane normal tothe aXis of "the abrading member after it is assembled.

Turning now to Figures 4 and 5, it will be observed that each or thewedge members 42 and 44 is open at the thin side over an angle on theorder of about 60.

The said openings at the thin sides of the Wedge membars are availed. offor mounting the abrasive segments 54 about the hub 38 according to myinvention. This is brought out in Figures 4 and 5, wherein it will beseen that each of the abrasive segments 54 extends partially around theperiphery of the abrading. member. Each "6 abrasive segment has its openside arranged diametricallyopposite to the open side of the adjacent ofthe wedge members 42, 44. Further, each abrasive segment is arranged sothat it lies on one face of the adjacent wedge member on one side of theopening in the wedge member, and in the opposite face thereof, on theother side of the said opening.

Thus, the abrasive segments and the wedge members are, in effect,threaded together, one pair in a right-hand direction and then the nextpair in a left-hand direction, and so on until all of the abrasivesegments and the corresponding wedge members have been brought togetherand mounted on the cylindrical hub 38. At this time the bolts 52 arepassed through apertures provided therefor in the wedge members andabrasive segments, and the entire assembly is made rigid by drawing thebolts up tight. I

The resulting assembly is best illustrated at the right side of Figure4, and in Figure and in Figures 7 and 8. In these figures it will beobserved that what is provided is an abrading member having abrading ribmeans extending therefrom. These rib means comprise segments of abradingmaterial arranged in paths which spiral about the member in right andleft-hand helixes. Each rib memher is discontinuous at alternate pointsof intersection of the spiral path thereof with the spiral path of theother rib means. Figure it will be noted shows one end point 64 of thefirst portion of the right-hand rib 60 disposed substantially midwaybetween the end points 66 of the nearest adjacent segment of theleft-hand rib 62. Similarly with each end of each segment of the tworibs inwardly of the ends of the work member.

While the rib members 60 and 62 in Figure 10 have been shown to comprisesubstantially true helices, and in which casethe individual spots formedby the segments of the ribs would be in the form of straight diagonallines, the explained manner of forming the wedge members 42 and 44 bysurface grinding the opposite faces thereof to flat surfaces holds theabrasive segments in a form which is not a true helix. Rather, the endportions of the abrasive segments are supported at substantially truehelix angles, while the center portion of each abrasive segment is heldin an almost straight circumferential path. This can be seen in Figure7, wherein the center portion 68 of the segments will be seen to ex tendin substantially a straight circumferential direction, whereas the endportions of the segments form nearly a true helix.

Because of the described departure from a true helix of the abrasivesegments, each of the individual spots illustrated in Figure 3 has aslight offset in the center, the said center part of the spot, ofcourse, corresponding to the described center, portion :of the abrasivesegment by which it is formed. It will be understood that if the wedgeswere formed to support the abrasive segments at a true helix angle, thenthe spots would be perfectly straight and would not have the indicatedoffset in the center. The wedge members could readily be formed in thismanner as by a cam operated grinder or the like, but the exact manner inwhich the wedges are machined forms no essential part of the presentinvention. It is within the scope of this invention to provide a solidhub having helical slots formed therein for receiving the segments, ifso desired, and exactly equivalent results so far as the spotting of thesurface being machined would obtain.

Figure 9 shows one of the abrasive segments in developed form, andtherein it will be clearly seen that the end portions 70 of the segmentextend at different angles from the center portion 68.

In operation, thebuilt-up abrading member is mounted on the spindle ofthe wheelhead or is built-up directly thereon, and then is preferablytrued, asby a diamond,

and then is set in motion at the proper grinding speed.

The table 12 of the grinding machine is positioned so that work member Wis spaced longitudinally from the abrading member and the wheelhead andtable are adjusted relatively in height to bring the surface to beWorked and the wheel into proper grinding relation to provide for theproper depth of spots. The valve 26 is then actuated to provide for onesingle traversal of the abrading member across the surface to bespotted. This constitutes the entire spotting action and the work membercan then be removed.

In the machining of individual work members, such as the detachable waysfor machine tools, surface plates, and the like, the work member wouldbe mounted on the table of a machine about as illustrated in Figure 1,and the grinding operation carried out as described. In other cases, as,for example, a lathe bed with the ways integrally formed thereon, thefinal finishing operation on the ways of the bed would probably becarried out in a way grinding machine having wheelheads positioned togrind all of the way surfaces. In an arrangement of this type, theregular way grinding wheels would be replaced by an abrading memberaccording to this invention for the spotting operation or an auxiliaryspindle could be provided, and the ways spotted after the finishingoperations on the ways had been completed in the way grinding machine.

The uniformity of the spot pattern is illustrated in Figure 3, and inFigures 12 and 13 the uniformity of depth of the individual spots isillustrated, as well as the formation at the end of each spot. In Figure12, the individual spots are indicated at 72, and it will be observedthat they are all exactly the same depth. The advantage obtaining fromthis is not only a uniform appearing spot pattern, but also absolutelyuniform lubrication over the entire spotted surface.

One of the spots is illustrated at enlarged scale in Figure 13.

The arrangement described up to this point has been for the purpose ofworking a fiat surface, but my invention can also be used for spottingV-ways, as will be seen from Figures 14 and 15.

In Figure 14, the work member W has the V-way 76 thereon with a spotpattern according to my invention, and for working this surface, I mayutilize the wheel illustrated in Figure 15, which has a V-shapedperiphery 78 which has been crush formed by a properly shaped roll so asto have right and left hand spiralling ribs 80 projecting therefrom.

In certain instances, it may be sufficient merely to provide a pluralityof uniformly distributed spots on a surface without making the spots orthe patten thereof, of such a nature that no straight line can be drawnacross the surface without intersecting the spots, as is the case withthe Figure 3 spot pattern. Such a spot. pattern is illustrated in Figure18, wherein the work member W has the distributed spots 82 formedthereon. This spot pattern can be produced by the wheel of Figures 16and 17, and which comprises a holder 84 having a. helical slot 86therein for receiving the segments 88, the outer peripheries of whichare interrupted, as at 90, to provide for the spaced surface workingareas that will provide the spot pattern of Figure 18. As will be noted,the helical rib means are made up of segments, each of which extendsabout 360? of the periphery of the holder and has thus a work memberwhich can be manufactured by conventional methods.

The holder 84 in Figures 16 and 17 is provided with the continuousspiral or helical slot 86, and the abrasive segments 88 can each consistof an annular disk cut through at one side, except for the end portionsof the abrasive rib which might consist of less than 360 about theholder. The segments are mounted on the holder by threading them intothe groove or slot 86, and they can be cemented or clamped therein asmay be desired in order to permit rotation of the holder at grindingspeeds without the segments becoming dislodged therefrom.

Still another manner in which an abrading. member according to myinvention can be constructed is shown in Figure ll in which the abradingmember comprises a body portion 92 with rib por-itons 94 of abradingmate rial secured thereto so that the rib portions follow spiral pathsas has been previously explained in connection with the othermodifications. Body 92 does not constitute any abrasive material, and ifof a rigid material,- such as ceramic or metal or glass, will have theabrading ribs 94 projecting outwardly from the outer periphery thereof.The body member 92 could also be made of a resilient material such as anatural or synthetic rubber or an elastorneric plastic and in this eventthe abrading ribs could have their outer extremities substantially flushwith the surface of the body member. The body member may advantageouslybe of a moldable or castable material in which case the abrading .ribs v94 would be supported in a suitable mold cavity or recess and thematerial of the body cast thcreabout. However, the body portion could beformed either by molding, casting or machining so as to have spirallinggrooves in the periphery thereof for receiving the abrasive rib members94 to be bonded thereto by any suitable adhesive. An advantage thatobtains from the practice of my invention, separate and apart from thelubricating or surface interrupting characteristics of the spot patternimparted to the surface, is the fact that the regularity and uniformityof the spot pattern imparts a pleasing appearance to the treatedsurface.

Further, with the surface interrupted by the spot pattern, minorirregularities therein which are of absolutely no consequencemechanically, but which would fatally detract from the work membervisually, are hidden, and the work members which might otherwise bescrapped can be utilized as first-class articles of manufacture.

in this connection, it is conceivable that my invention may be practicedfor no other purpose except to provide surface ornamentation for a workmember, such as a saw blade or the like. In this case, the individualspots of the pattern would have substantially-no depth, and the naturalresult of the practice of this invention would be to produce workmembers much more pleasing in appearance, and in which inconsequentialsurface blemishes would be hidden.

'The actual depth of the spots which I provide for the purposes oflubrication, as in connection with machine tool ways, or for surfaceinterruption, as in the case of a surface plate, may vary widely as,-for example, from, say, .00005 to .002. For pure surface ornamentation,of course, the spots might have a substantially unmeasurable depth,although it will be understood in the particular case of a saw blade, orsimilar working member, the spots might have sufficient depth to retaina lubricant to similar advantage.

As a specific example? of'one wheel construction and machiningarrangement for spotting ways a wheel constructed as indicated in Figure4 was employed with the wheel being about twelve inches in diametermeasured to the outermost portion of the abrading ribs. Each ribextended around about 270 of the circumferential extent of the wheel andhad a lead of about one-half inch.

With the wheel head motor operating at a speed of about 1800 R. .P. M.,it will be evident that the time required for the wheel to rotatethrough the angle about which one of the segments extends, namely,two-thirds of a revolution will be one-forty-fifth of a second.

If the spots formed on the workpiece by the abrasive action of the ribsare to extend across the workpiece at an angle of about 45, then theworkpiece will move relative to the wheel, so that it travels a distanceequal to the lead of one of the ribs, about one-half inch, in the samelength of time that the wheel is moving through the angle about whichthe rib extends, namely, on the order of one-thirtieth of a second.

In one second, therefore, the workpiece will move fifteen inches,andthis speed, converted to the more customary units of feet per minuteis seventy-live feet per minute. This speed of movement of thegrindingmachine table is a speed which can be attained by practicallyall machines.

The wheels illustrated in Figures 19 and 20 are characterized in beingformed with right and left hand grooves therein, thus forming raisedelongated diamond-shaped portions .between the grooves which form theactual spot pattern. p X v p In Figure 19, for example, the wheel isformed with a right-hand double start helical groove which isintersected by a left-hand double start helical groove 102. Thesegrooves are formed in the periphery wheel by use of a wide diamond andregulation of the rate of rotation of the wheel and the transverse feedof the diamond during a dressing operation to produce the grooves sothat they will have the properlead.

In Figure 19 it will be evident that there is formed about the wheel aplurality of elongated diamond-shaped raised portions 104, and when thewheel is rotated at a predetermined speed and the workpiece to bespotted is driven linearly relative thereto ata predetermined speed, apattern of elongated spots 106 will be formed on .the workpiece. Theraised areas 108 on the workpiece between the spots provide the bearingsurface for supporting the part bearing on the way surface. It will beevident that the particular size of the spots and the spacing thereoffrom each other could readily be controlled by controlling the width ofthe groove formed in the periphery of the wheel, whereby the properratio of bearing area to oil spot area can be maintained.

In Figure 20 a wheel substantially the same as illus trated in Figure 19is shown, except that therightand left hand helical grooves 110 and 112are single start instead of double start, and this results in the raiseddiamond-shaped arrangement 114, being substantially more elongated thanthose of Figure 19. The same sort of spot pattern would be imparted tothe workpiece by both wheels. The illustration in Figure 22 shows aworkpiece 116 having spots 118 thereon, each of said spots being formedby an elongated diamond-shaped segment of the grinding wheel, and one ofwhich segments is illustrated in Figure 22 at 120 as cut ofi from thewheel.

'In practice, the arrangement of Figures 19 and 20 is employed inthefollowing manner; a machine tool bed is first planed to bring the wasurfaces thereof to within a certain limit over their finished size. Themachine tool bed is then mounted on the table of a grinding machine withthe way sections aligned with the machine so that a minimum amount ofstock has to be removed from the actual way section.

The ways are then ground at regular grinding speed, including rough andfinish grinding cycles, and with the Wheel that accomplishes thegrinding being trued in the usual manner to provide for the properaccuracy and quality of finish.

After the ways have been ground in the described manner to the properaccuracy, size and finish, the grinding wheel is then dressed to formthe right and lefthand spiral grooves in the periphery thereof asdescribed above. At this time the grinding wheel will be running atreduced speed and the diamond will be'reciprocated transversely of thewheel during the dressing operation. 7

The spiral grooves formed in this manner will be about .003 to .005inches in depth. 7

After the wheel has been dressed to form the grooves thereon, the wayscan then be spotted in the manner which has been described previously byoperating the wheel at grinding speed anddriving the bed past the wheela single time and at a predetermined speed for 7 each surface that is tobe spotted.

Thereafter, the bed is removed from the grinder and another bed to beworked is placed thereon. At

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9 time it will not be necessary to true off the grooves of the grindingwheel, as they will be worn down materially during the rough grindingopsration and will be substantially completely removed at the. time oftrueing the wheel for the finishgrinding operation.

It will be understood that this invention is susceptible to modificationin order to adapt it to different usages and conditions, and,accordingly, ittis desired to comprehend such modifications within thisinvention as may fall within the scope of the appended claims.

I claim:

1. In an arrangement for working a smooth surface to form a spot patternthereon; a support for the workpiece having the said surface, arotatable abrasivemernber for working the surface, said membercomprising a holder forming the hub of the wheel, abrasive segmentsmounted in said holder, one series of said segments forming a right handspiral rib on the holder interrupted between the ends of adjacentsegments, and another series of said segments forming a left hand spiralrib on the holder interrupted between the ends of adjacent segments, theinterruptions in the respective ribs being opposite each other, meansfor rotating the abrasive member at a predetermined speed, and means forreciprocating said support and member relatively at a predeterminedspeed.

2. In an arrangement for working a smooth surface to form a spot patternthereon; a support for the workpiece having the said surface, arotatable abrasive member for working the surface, said membercomprising a holder forming the hub of the wheel, abrasive segments mountedin said holder, one series of said segments forming a right hand spiralrib on the holder interrupted between the ends of adjacent segments, andanother series of said segments forming a left hand spiral rib on theholder interrupted between the ends of adjacent segments, each segmentextending around the member for at least 180", the interruption in therespective ribs being opposite each other, means for rotating theabrasive member at a predetermined speed, and means for reciprocatingsaid support and member relatively at a predetermined speed.

3. In an arrangement for working a smooth surface to form a spot patternthereon; a support for the workpiece having the said surface, arotatable abrasive member for working the surface, said membercomprising a holder forming the hub of the wheel, abrasive segmentsmounted in said holder, one series of said segments forming a right handspiral rib on the holder interrupted between the ends of adjacentsegments, and another series of said segments forming a left hand spiralrib on the holder interrupted between the ends of adjacent segments,each segment extending around the member an angular distance not lessthan 180 up to about 300", the interruption in the respective ribs beingopposite each other, means for rotating the abrasive member at apredetermined speed, and means for reciprocating said support and memberrelatively at a predetermined speed.

4. In an arrangement for working a smooth surface to form a spot patternthereon; a support for the workpiece having the said surface, arotatable abrasive member for working the surface, said membercomprising a holder forming the hub of the wheel, abrasive segmentsmounted in said holder, one series of said segments forming a right handspiral rib on the holder interrupted be tween the ends of adjacentsegments, and another series of said segments forming a left hand spiralrib on the holder interrupted between the ends of adjacent segments,each segment extending around the member an angular distance not lessthan 180 up to about 300, the interruptions in the respective ribs beingopposite each other, means for rotating the abrasive member at apredetermined speed, means for reciprocating said support and memberrelatively at a predetermined speed, each said s t having a ead g rcdeetm aedaai unt m 10 end to end, and the speed of relative reciprocationof the support and member being such that the support moves relative tothe member an amount about equal to said lead while the member rotatesthe angular distance of one segment.

5. A rotary abrading member of the nature described; means forming a hubfor said member adapted for connection with a spindle, means on the hubforming right and left hand spiralling groove means, and abrasivesegments mounted in said groove means and forming discontinuous rightand left hand spiralling abrasive rib means.

6. An abrasive member of the nature described; a cylindrical hub adaptedfor mounting on a spindle, a plurality of annular wedge members mountedon said cylindrical hub and defining right and left hand spirallinggroove means, and abrasive segments mounted in said groove means anddefining right and left hand spiralling discontinuous abrasive ribmeans.

7. An abrasive member of the nature described; a cylindrical hub adaptedfor mounting on a spindle; a plurality of annular wedge members mountedon said cylindrical hub and defining right and left hand spirallinggroove means, abrasive segments mounted in said groove means anddefining right and left hand spiralling discontinuous abrasive ribmeans, said hub comprising a radial flange at one end, and a clampingring at the other end for clamping said wedges and abrasive segmentstogether.

8. An abrasive member of the nature described; a cylindrical hub adaptedfor mounting on a spindle, a plurality of annular wedge members mountedon said cylindrical hub and defining right and left. hand spirallinggroove means, abrasive segments mounted in said groove means anddefining right and left hand spiralling discontinuous abrasive ribmeans, said hub comprising a radial flange at one end, a clamping ringat the other end for clamping said wedges and abrasive segmentstogether, all of said wedge means having the same included angle betweentheir opposite faces, and there being adapter wedge means adjacent eachof said flange and clamping ring having half the said included anglebetween their opposite faces.

9. In an abrasive member of the nature described; a cylindrical hubportion having a radial flange at one end and adapted for mounting on aspindle for being driven in rotation, a plurality of annular wedgemernbers open at their thin sides mounted on said hub so that adjacentof the said wedge members have their open portions positioneddiametrically opposite each other, a plurality of annular abrasivesectors open at one side mounted between said wedge members, each sectorhaving its open side diametrically opposite the open side of theadjacent wedge member and being disposed with one end on one side of thewedge member and its other end on theother side of the wedge member, andmeans for clamping said wedge members and segments against said flange.

10. In an abrasive member of the nature described; a cylindrical hubportion having a radial flange at one end and adapted for mounting on aspindle for being driven in rotation, a plurality of annular wedgemember s open'at their thin sides mounted on said hub so that adjacentof the said wedge members have their open portions positioneddiametrically opposite each other, a plurality of annular abrasivesectors open at one side mounted between said wedge members, each sectorhaving its open side diametrically opposite the open side of theadjacent wedge member and being disposed with one end on one side of thewedge member and its other end on the other side of the wedge member,and means for clamping said wedge members and segments against saidflange, said clamping means comprising a clamping ring on the end of thehub opposite the said flange and clamping bolts extending throughsaid-ring, wedge members, and segments into saidflange.

11. in an abrasive member of theinature described; a cylindrical hubportion having a radial flange at one end and adapted for mounting on aspindle for being driven insrotation a plurality of annular wedgemembers open at their thin sides mounted on said hub so that adjacent ofthe said wedge members have their open portions positioned diametricallyopposite each other, a plurality of annular abrasive sectors open at oneside mounted between said wedge members, each sector having its openside diametrically opposite the open side of the adjacent wedge memberand being disposed with one end on one side 'of the Wedge member andits. other end on the other sideof the wedge member, and means forclamping said wedge members and segments against said 'flan'gc, saidclampingmeans comprising a clamping ring on the end of the hub oppositethe said flange and clamping .bolts extending throughsaid ring, wedgemembers, and segments into said flange, there being an adapter wedgemember adjacent said clamping ring and also adjacent said flange, eachhaving half the included angle or thefirst-rnfentioned wedge members,whereby the planes of symmetry of .saidfirstementioned wedge members areperpendicular to the axis of said hub.

12. An arrangement as set forth in claim 9 in which each wedge member ison the orderof one-half inch thick at the thickest part and eachabrasive sector is about 270 in extent.

13. An arrangement as [set forth in claim 1 in, which means are providedfor halting the relative reciprocation of the support and membe afterone traversal thereof.

14. An arrangement asset forth in claim 1 in which means are providedfor adjusting the said predetermined s eed of relative reciprocation ofsaid support and member.

15. The method or grinding whereby one and the same Wheel is utilizedfor both finish grinding and for grinding a spot pattern on a workpiececomprising; trueing the eriphery of the wheel to a smooth. workingsurface, and reciprocating the workpiece and wheel relatively for anormal grindin operation, tracing shallow grooves in the'whee'l to formspaced upstanding areas thereon, reciprocating the workpiece relative tothe wheel at a second predetermined speed and for a single pass toimpart a spot pattern" tothe ground surface thereof, and repeating thesteps for subsequent workpieces for a repetitive cycle of operations.

16. In an arrangement for working a smooth surface to form a spot v'aa'ttern thereon; a support for the workpiece having the said surface,a rotatable abrasive incinber for working the surface, said membercomprising rib means of abrasive material projecting from said memberand arranged in right and left hand spiral pains, each said rib meansbeing discontinuous at each alternate point of intersection of the saiaspirai path pertaining thereto with the Spiral path of the other hand,means for rotating said member at working speed, and means tor movingsaid support and member relatively linearly at such a speed that eachsegment of each rib means abrad'es a portion of said workpiece entirelyseparate from the portion of the workpiece abraded by the others of thesaid segments. g

17. In an arrangement for working a smooth surface to form a spotpattern thereon; a sup ort for the workpiece having the said surface, arotatable abrasive memher for working the surfac said merilbe'rcomprising a hub portion for being secured to a spindle and having aperipheral surface parallel to the surface to be spotted,

abrasive areas on said peripheral surface defining spaced segments ofright and left hand spirals, each such spiral extending the full aXia'llength of said abrasive member,

means for rotating said member at working speed, and

means :for moving said member and workpiece "linca'rlyat 'such a speedthat each said segment abrades' a portion of said workpiece entirel searate from the portion abraded byt'h'e others 'of said segments.

nature described; a

18. In an abrading wheel of :hub portion .adaptedsfor mounting on aspindle for being driven .in rotation, a peripheral working portion onsaid wheel and abrading means on said peripheral portion comprising ribmeans of abrading material arranged in right and left hand intersectingspiral paths, each said means extending the full Saxiallength of saidwheel and at least one of .each rib means being discontinuous at eachpoint of intersection of the spiral path pertaining thereto with thesaid spiral path of the other hand, said rib means being fiat and thinrelative to the space therebetween.

19 In an abrading wheel of the nature described; a hub portion adaptedfor mounting on a spindle for being driven in rotation, a peripheralworking portion on said wheel, and abrading means on said peripheralportion comprising rib ineansor abrading material arranged inintersecting right and left hand spiral paths, each said rib meansextending the full axial length of the wheel and each said 'rib meansbeing discontinuous at every alternate point of intersection of the pathof the said spiral path thereof with the spiral path of the other hand,said rib means being fiat and thin relative to the space th'erebetween.

20; The tneth'od of spotting a j'sm'oothly finished sur- .face toprovide for a regular and uniform spot pattern thereon "which comprises;rotating'at a predetermined spend an abra'ding wheel member havingdiscontinuous upstanding abrading surfaces thereon arranged in right andleft hand spiral paths with the discontinuities of the s'aid'ribsoccurring at the points of intersection of the said 'pathsth'ereof,moving the surface to be worked and the abradin'g wheel memberrelatively at a predetermined speed with the-wheel member-in contactwith the surface, and halting the said relative movement after onecomplete traversal of the surface to be worked by the said abradingwheel member.

21. The method of "spotting a smoothly finished surface to provide for aregular and uniform spot pat-tern thereon which comprises; rotating at apredetermined speed an abra'din'g wheel member having discontinuousnpstanding-abra'ding surfaces thereon arranged in right and left handspiral paths with the discontinuities of the said ribs occurring at thepoints of intersection of the said paths thereof, moving the surface tobe worked and the 'abrading wheel member relatively at a predeterminedspeed with the Wheel member in con-tactw-ith the surface, and haltingsaid relative movement after one complete traversal or the surface to beworked by the said abradin'g wheel member, the speed of the saidrelative movement being so selected relative to the speed of rotation ofsaid abradin'g wheel member that the said surface and abrading wheelmember rnov'e relatively about the same distance as the lead of one ofthe segments of said ribs in the interval that the said abradirrg "wheelmember rotates through the angle occupied by one of said segments.

A method of grinding a machine tool way or similar surface to provide atrue bearing surface having a pattern of oil Isp'ots thereon with oneand the same grinding wheel which comprises; .trueing the periphery of a.gr inding wheel to .a smooth working surface, grinding the way to asmooth finish with the trued grinding wheel, dressing right and lefthand spiralling grooves in the periphery of the "grinding wheel thusforming on the Wheel a regular pattern of raised spots, and making asingle pass along the lengthof the way with the dressed grinding wheelwith therelat-ive lineal speed between the wheel way in relation to therotational speed of the wheel being such that each area ground by eachsaid raised spot is independent from all other such areas.

H 23. A method of working a machine tool way or the like to provide asmooth bearingsurface thereonv having an oil spot pattern with one andthe same grinding wheel which comprises; inn ng a grinding wheel to asmooth warring surface, grinding the way with the trued grinding wheelto the desired finish and accuracy, reducing the spe'ed o'f thegrinding' an, dressing right and left liand spiralling groove in theperiphery of the grinding wheel thus forming on the wheel a regularpattern of raised spots, runningthe grinding wheel at grinding speed,and taking a single pass along the finished way with the dressedgrinding wheel with the relative lineal speed between the work and wheelbeing great enough that the said raised spots grind spaced areas on thework whereby a spot pattern is imparted to the surface of the way.

24. In an abrading wheel of the nature described; a hub portion adaptedfor mounting on a spindle for being driven in rotation, a peripheralworking portion on said wheel, abrading rib means upstanding from theperiphery of the wheel, said rib means arranged in intersecting rightand left hand spiral paths, each said rib means being discontinuous atevery alternate point of intersection of the said spiral path thereofwith the spiral path of the other hand, each said rib means extendingfor about 270 about the said wheel between consecutive points ofdiscontinuity of the said rib means, each rib means having a lead ofabout one-half inch between the said consecutive points of discontinuitythereof, and said rib means being flat and thin relative to the spacetherebetween.

25. In an abrading wheel of the nature described; a hub portion adaptedfor mounting on a spindle for being driven in rotation, a peripheralworking portion on said wheel,

said working portion comprising abrading means consisting of right andleft hand spiral rib means upstanding from the periphery of the wheel,each said rib means being discontinuous at every alternate point ofintersection, a section of the spiral path thereof with the spiral pathor the other of said rib means, the said peripheral portion of saidwheel being V-shaped in cross section.

References Cited in the file of this patent UNITED STATES PATENTSTripler Apr. 29, 1879 Schrebler May 29, 1883 Maloy Aug. 31, 1886Cunningham Apr. 1, 1890 Whitaker May 21, 1895 Jones Oct. 6, 1896 ShermanMay 23, 1899 Smith Mar. 19, 1907 Elston Nov. 9, 1920 Canning June 3,1924 Olson July 15, 1924 Hatz Nov. 10, 1925 Burgess Aug. 19, 1930 PattonDec. 23, 1930 Sandler Oct. 18, 1932 Leis May 9, 1933 Kosfeld Oct. 9,1934 Sart May 28, 1935 Ruppert Dec. 15, 1936 Webber June 8, 1943 WilsonFeb. 24, 1948 Peckett Sept. 28, 1948 FOREIGN PATENTS Great Britain Nov.4, 1936 Germany Dec. 15, 1944

